Apparatus for production of cast concrete members

ABSTRACT

Prestressed cast concrete structural members which are T-shape or multiple T-shape in cross section are cast in a metal mold. Each T portion of the mold comprises inverted L-shape form members, the depending portions of which have pin members affixed thereto. The pin members are cooperatively received in diagonal slots of a horizontally movable cam plate. Movement of the cam plate causes the depending portions to move laterally away from one another to enable stripping of the cast member from the form. A separately constructed vertically movable horizontal pallet member forms the bottom surface of the form and includes a roller transfer assembly supported on an elevator mechanism. By cam action, the cast member is raised and then transferred to a roller conveyor which engages the bottom surfaces of the extending arms of the cast member. The roller conveyor transfers the member to another work area.

United States Patent [191 7 Leonard et a].

[111 3,832,118 Aug. 27, 1974 APPARATUS FOR PRODUCTION OF CAST CONCRETE MEMBERS v [75] Inventor: William E. Mitchell, Franklin,

Tenn.

[73] Assignee: Span-Deck, INC., Franklin, Tenn. [22] Filed: May 8, 1972 [21] Appl. No.: 251,358

[52] US. Cl 425/443, 249/74, 249/161,

425/452 [51] Int. Cl B28b 7/10 [58] Field of Search 425/442, 443, 452; 249/162, 161, 74

[56] References Cited UNITED STATES PATENTS 1,068,613 7/1913 Volz 249/162 X. 1,642,947 9/1927 Fischer 425/442 X 1,770,368 7/1930 Fahlman 249/162 X 2,916,795 12/1959 Henderson..... 249/26 3,132,403 5/1964 Richards et a1 249/50 3,168,771 2/1965 Nelson 249/50 3,217,375 11/1965 Kinnard 425/130 I30 I33 I 3,523,343, 8/1970 Mitchell 425/88 Primary Examiner--Richard B. Lazarus Attorney, Agent, or Firm-Cameron, Kerkam & Sutton ABSTRACT Prestressed cast concrete structural members which are T-shape or multiple T-shape in cross section are cast in a metal mold.- Each T portion of the mold comprises inverted L-shape form members, the depending portions of which have pin members affixed thereto. The pin members are cooperatively received in diagonal slots of a horizontally movable cam plate. Movement of the cam' plate causes the depending portions to move laterally away from one another to enable stripping of the cast member. from the form. A separately constructed vertically movable horizontal pallet member forms the bottom surface of the form and includes a roller transfer assembly supported on an elevator mechanism. By cam action, the cast member is raised and then transferred to a roller conveyor which engages the bottom surfaces of the extending arms of the cast member. The roller conveyor transfers the member to another work area.

31 Claim, 10 Drawing Figures PATENIEB msznan smear? I28 i I PATENTED mfizm" SIEU 5K 7 APPARATUS 'FOR PRODUCTION OF CAST CONCRETE BACKGROUND OF THE INVENTION This invention relates to the manufacture of cast concrete structural members, hereinafter sometimes referred to as T slabs or double T slabs or in the interest of brevity simply as slabs, and is more particularly concerned with an improved apparatus for producing such slabs more efficiently and at less cost than has been possible by utilization of apparatus heretofore available.

In the casting of concrete structural members mold forms are usually employed which are open at the top for reception of the fluid concrete mix. When the fluid concrete mix is set and the cast product is to be removed from the mold, it must be possible to establish clearance between the product and the sidewalls of the mold to strip the product therefrom. This stripping clearance heretofore has been obtained by a variety of ways.

In one form of known prior art arrangement, a device is connected to the upper end of the mold sidewall and adapted to draw the sidewall away from the molded product. Such a device is suitable for cast columnar members, however, in the case of concrete T-slabs access to the side walls is denied by virtue of the continuous outwardly extending cast surfaces (arms of the T) which are cast above the forms.

In T-molds, resort has been made to complex mechanical mechanisms for the purpose of stripping the side form members from the T-mold. Typicalmechanisms are illustrated in U.S. Pat. Nos. 3,168,771 and 3,132,403. Although such mechanisms are suitable for the use intend ed, economics of manufacture demand operating mechanisms which are simple in design and thus less costly and which enable quick transport of the cast member away from the casting location so that another slab can be readily cast at the same location.

The apparatus embodying the present invention is particularly adapted for use in making concrete structural members in accordance with either a fixed bed process of the type described in U.S. Pat. No. 3,217,375 or a movable bed process of the type described in U.S. Pat. No. 3,523,343. In Pat. No. 3,217,375, the structural member is formed on a stationary casting bed by means of hopper and roller units which travel the length of the bed, after which the remainder of the structural member, including the core openings therein, is produced by a casting machine which also moves along the bed. The completed member is then cured and subsequently cut into desired lengths. Such a process is commonly referred to as a stationary bed process.

U.S. Pat. No. 3,523,343 describes a moving bed process wherein a manufacturing area contains sequentially used items of production equipment suitably housed and located centrally'between an elongated curing area and a similarly elongated unloading overrun area. A casting bed moves back and forth several times during each production cycle while the various operations of the manufacturing process are performed. The casting bed comprises a lengthy stress frame which is mounted on a track extending the full length of the facility and carries a molding form in normally remains stationary in the manufacturing area while the bed moves beneath it. The casting bed is moved along the track at any desired speed in either direction by suitable driving means such as two sets'of selectively operable hydraulic motors which are located on opposite sides of the manufacturing area and which drive rubber tired wheels having frictional engagement with the stress frame.

SUMMARY OF THE INVENTION The present invention is advantageously suitable for use in either the stationary bed process or the movable bed process and resides in the structural arrangement of the molding apparatus and the manner in which the molded concrete slab is stripped therefrom. To this end it is a primary object of the present invention to provide an improved molding apparatus which facilitates the stripping of precast slabs from the mold.

Another object of the present invention is to provide an improved apparatus for the production of cast concrete members which reduces to a minimum the time and labor required to manufacture the cast members and to strip the molded product from its mold.

The apparatus of the present invention is characterized in that prestressed concrete slabs which are T- shape or multiple T-shape are cast in forms comprising inverted L-shape sections closed at the bottom by a horizontal pallet or form member. The horizontal form member includes supporting rollers adapted to ride on an elevating mechanism assembly having a downwardly extending cam follower. The cam follower is adapted to cooperate with a longitudinally driven stepped cam.

' posed in a horizontally movable cam plate. Upon completion of casting, movement of the cam plate causes relative movement between the side forms and the cast T-member which is sufficient to spring the side forms clear of the cast member and permit stripping of the cast member from its form. After the side forms are sprung, the stepped cam is actuated to cause the slab to be raised above the form and transferred by the supporting roller assembly to a roller conveyor disposed beneath the extending arms of the cast slab. The roller conveyor transfers the slab to a storage or other work area.

The preferred embodiment of the invention described herein relates to the formation of cast slabs which are multiple T-shape in cross section formed in a moving bed process. It should be understood, however, that the inventive concept is also applicable to the manufacture of other forms of structural members including a vertically disposed cast section formed between two vertically disposed wall members and that the term structural member as used herein is not limited to load-bearing members, but also includes such other precast elements as wall panels, partitions, column covers and like. By way of explanation, the appawhich the concrete member is cast by equipment which I BRIEF DESCRIPTION OF THE DRAWINGS The invention may be more readily understood by reference to the following drawings wherein like parts are identified by like reference characters throughout the several views and wherein:

FIG. 1 is a diagramatical layout of a rolling bed process for manufacturing cast concrete members in accordance with the present invention;

FIG. 2 is a fragmentary, perspective view of a double T slab formed by the apparatus embodying the present invention;

FIG. 3 is a plan view of a casting bed with certain parts broken away;

FIG. 4 is a sectional view of the system taken along line 44 of FIG. 1 with the walls of the kiln broken for clarity;

FIG. 5 is a sectional view of the kiln taken along line 5-5 of FIG. 1;

FIG. 6 is a cross sectional view of a composite form for casting a triple T-slab in accordance with the present invention;

FIG. 7 is a bottom view of the form release shown in FIG. 6;

FIG. 8 is a side view of the elevating mechanism taken along lines 88 of FIG. 6;

FIG. 9 is a partial side elevational view of the slab supporting roller conveyor; and

FIG. 10 is a partial side elevational view of the elevating assembly with a cam movement stop mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIG. 1, there is diagramatically illustrated therein the layout of a rolling bed process or facility for manufacturing cast concrete members embodying the present invention which comprises a main manufacturing building 10, of sufficient size to accommodate substantially all of the production equipment. At one,end of building 10 (the left hand end as viewed in FIG. I) is provided a curing station or area I]. The curing area may take the form of a kiln 12 of Quonset type construction having a length much greater than that of the main building 10 and sufficient to contain an elongated casting bed indicated generally at 14. At the other end of the main building opposite the kiln 12, there is provided an overrun area 13.

At the other end of the kiln 12, there is provided a product storage area 15 where the cast members are stripped from their forms. The product storage area includes a roller conveyor 16 for transferring stripped slabs from the kiln .12 to a saw house 18 where the slabs may be cut in convenient lengths. Beyond the saw house is a further roller conveyor 20 and crane access 19 area wherein a suitable overhead crane 21 transfers cut lengths of the slab to a storage yard.

Passing centrally through the main building and extending the full length of building 10, kiln I2, overrun area 13, roller conveyor 16, saw house 18 and roller conveyor 20 is a fixed track 22, consisting of a pair of laterally spaced iron rails on which casting bed 14 is adapted to be rolled back and forth, passing through the main building several times during each production cycle. The bed 14 is moved along the track 22 by driving units indicated generally at 24, 26, located at suitage area .15. Other locations could, of course, be utilized. A stationary winch 25 located between the exit to the kiln and the saw house is provided to remove the cast product and onto the roller conveyor 16.

In a typical installation the overall plant length, that is the length of fixed track 22 is approximately l,7l0 feet. The casting bed 14 extends approximately 480 feet, while main building 10 has a length of approximately I00 feet parallel to track 22 and extends approximately 30 feet on each side of the track. The length of the curing kiln I2 is approximately 500 feet, as is the length of the roller conveyor 16, between the kiln and the saw house. The roller conveyor extends slightly into the saw house so that its overall length is about 525 feet. The saw house has a length in the order of feet parallel to track 22 and extends some 10 feet to each side of the track. The roller conveyor 20 adapted to receive the cut pieces from the saw house extends from within the saw house to a distance beyond of some 80 feet and its overall length is about 100 feet. The overrun area to the right of the main house 10 as viewed in the drawing extends for a distance of approximately 500 feet.

Although, as indicated above, the broad concept of the present invention is applicable to a wide variety of precast concrete members, the facility illustrated in the accompanying drawing is particularly adapted to manufacture of pre-stressed concrete slabs which are T- shape or multiple T-shape in cross section of the form illustrated in FIG. 2. As there shown, the slab 28, comprises a flat top surface 29, having outwardly extending arms 30 and 31 and a central joining member 32 forming with arms 30 and 31 the flat top slab surface 29. Stems or leg members 33 and 34 depend from the bottom face of slab 28 to complete the structure.

As shown in FIG. 2, leg members 33, 34,each contain at least one beam stressing strand or cable 36, suitable in size and strength to provide the desired amount of pre-stress in the slab. Fr simplicity, only a single stressing cable has been shown in the lower portion of the stem; however, it should be reaily apparent that additional cables may be distributed along the stem and also along the arm members. The cables extend the entire length of the mold form and are anchored at one end and tensioned at the other end by a suitable tensioning or jacking device in a manner well known in the art. If desired, laterally extending reinforcing rods may be provided across the slab surface 29 to meet the ering concrete to a point above track 22 at which the able locations along the track, for example, at the exits to the main building 10 and at opposite ends of the storconcrete hopper of a main casting machine 42 is positioned when in use. The portion of building 10 on the opposite side of track 22 constitutes an equipment storage and transfer area 48 housing a plurality of tracks 50 parallel to but lying in a plane above the plane of track 22 in the manner described in US. Pat. No. 3,523,343. Equipment such as a main casting machine 42, a pallet cleaning and oiling unit 52, rolling unit 54 and other necessary production items are conveniently stored in area 48 when not in use.

Extending perpendicular to storage tracks 50 and intersecting main track 22 is a transfer track 51 on which is mounted a transfer car 53 adapted to move the various equipment units from and to storage tracks 50 and to and from normally stationary operating positions above the casting bed 14 as the latter moves along the track 22, as hereinafter described. The area between the rails of the transfer track 51 opposite the storage tracks 50 closest to the track 22 is excavated to provide a cleaning pit 56 having a drain 57 at which location the equipment units may be cleaned after use before being returned to storage. Also located in the storage and transfer area 48 adjacent track 22 within building is a main power unit 60 which provides hydraulic power to casting bed drive units 24, 26 and other elements of the installation hereinafter described. Positioned on the other side of the track 22 opposite the main power unit 60 is a control console 62 having suitable connections to power unit 60, drive units 24, 26 and other elements actuated by the power unit. The console 62 is so arranged that substantially all of the manufacturing operations involved in producing cast concrete T-slabs by means of the apparatus of the present invention can be either directly controlled or supervised by the operator of the console.

Referring now to FIG. 3 in addition to FIGS. 4-6, the casting bed 14 comprises a massive elongated stress frame 68 made up of longitudinally extending members 70, cross members 72 and diagonal members 74 which form a base extending the full length of the casting bed with the cross members 72 projecting outwardly on each side beyond longitudinal members 70. Mounted on the ends of cross members 72 are a pair of longitudinally extending side members 76 in the form of vertically positioned I beams, on the upper surface of which are mounted a pair of angle iron rails 78 extending the full length of the casting bed adapted to support the various units of production equipment previously mentioned while the casting bed is moved to and fro in the main building. Mounted beneath the cross members 72 of the stress frame by means of wheel brackets 80 are a plurality of wheels 81 which support the casting bed on the rails of the fixed track 22.

Within the space between side members 76, the stress frame carries the molding form 82. As most clearly shown in FIG. 6, molding form 82 comprises a pair of inverted L-shape metal form members 84, 86 and one or more inverted U-shape metal form members 88. As should be readily appreciated, the number of U- shape members used in the composite-form is determined by the desired cross sectional shape of the structural members. For a simple T-cross sectional slab, no U-shaped forms are necessary. For a double T-slab, a single U-shape form is required, for a triple T-slab, two U-shape forms are required etc. Because of the great lengths of the casting bed, it is preferable to divide each of the forms into sections of 10 to feet in length and to mount each section individually.

FIG. 6 illustrates a composite form 82 for casting a triple T-slab 128 comprising outer cantilever arm sections I30 and 131, intermediate section 132 and three depending leg members 133 forming an integral structure. Each L-shape form member includes a horizontally disposed arm supporting extension 83 and a vertically disposed leg forming section 85, the lower end of which may be turned over as at 87 to provide a shoulder or supporting ledge for stiffening members 89.

Members 89 are spaced lengthwise along the leg forming section and the several stiffening members are interconnected 'at their lower outer ends as viewed in FIG. 6 and reenforced by an angle iron bracket 90. Advantageously, bracket 90 has depending therefrom a plurality of pin members 91 spaced lengthwise thereof.

As most clearly shown in FIG. 7, pin members 91 are each received in an associated diagonal oriented slot 63 provided in a flat, horizontally disposed cam plate 64. Alternate slots are oppositely oriented or oblique to each other so that adjacent slots below a leg form are adapted to receive the pin members of the adjacent leg forming members. Thus, each leg forming section comprises a pair of vertically disposed form sections, each of which have depending pins received in corresponding oppositely oriented slots such that as cam plate 64 is moved in a horizontal plane, the force exerted on the pin members by the sides 66 and 67 of the adjacent slots 63 spring the vertical form sections outwardly.

Movement of the cam is effected by actuating arms 69 guided for movement in a horizontal plane in' channel section 71 supported to cross members 72 of the stress frame..Any suitable arrangement may be provided to effect actuation of arms 69. For example, suitable hydraulic cylinders may be provided having piston rods connected to arms 69 and cylinder connected to .main power unit 60 and control console 62 to effect is formed for the intermediate section 132 of the slab between the depending leg members 133 with the consequent advantages derived from standardization of parts. For convenience, leg and top slab forming sections of a U-shape member are identified with the same reference characters as the corresponding forming sec- 1 ing sections 85 depending therefrom by means of which pallets 92 may be translated in a horizontal plane while leg sections are sprung apart. To this end, wheels 98 are supported on a substantially horizontal platform 100 extending the length of pallet 92 and slightly below.

As hereinbefore described pallets 92 are supported for movement in a vertical plane as well as in a horizontal plane. To this end, platform 100 forms the elevating support for an elevating mechanism by which the cast member. is raised sufficiently such that the undersurfaces 134 of slab 128 supportingly ride on rollers 136 of roller conveyor 16.

As shown in FIG. 9, as well as FIG. 1, roller conveyor 16 is adapted to receive slab 128 as its leaves kiln 12. To this end, a stationary winch 25 provides product removal force for removing the cast product from the form. Conveniently, a cable may be fastened to an eye hook (not shown) mounted in the cast member so as to pull the slab free from the form, onto the conveyor 16. As the slab rolls along the roller bearing supporting rollers 136, the pallet 92 and supporting rollers 98 fall away from the under surface 135 of the leg members. A supporting platform 147 may be provided to receive and support the pallet and roller assembly as it falls free so that it may readily be returned to form 8 for the next casting operation.

The elevating mechanism is best shown in FIGS. 6, 8 and and comprises platform 100 adapted to be raised upon movement of cam follower 101 along the contoured surface 102 of cam 103. Platform 100 supports at spaced intervals a downwardly depending plate 104 having a central slot 105. Received within slot 105 is a bushing 10 6 which-supports a threaded shaft 107, the end of which is rounded in form and adjusted to bear against surface 102. Cam 103 comprises a flat surface 102 which is stepped to provide three distinct elevational positions 108, 109, 110. Each cam 103 is supported by a pair of side gussets 11.1 and 112 fastened to a slide rail 113. The outermost slide rails 113 are guided for movement in a horizontal plane by a pair of channel sections 114- and 115 supported beneath cross members 72. The centermost slide rail is rigidly mounted to an inverted channel member 116 which is in turn rigidly mounted by welding or the like to a drive beam 117.

As most clearly shown in FIG, 5, drive beam 117 is disposed to be engaged by a pivotally supported drive wheel assembly disposed in a pit 119 located between tracks 22 adjacent exit of kiln 12. Drive wheel assembly 118 includes a friction engaging rubber tired wheel 120 which may be selectively positioned in and out of contact with beam 117. Wheel 120 is driven by a reversible, variable speed hydraulic motor 121, the output shaft 122 of which is connected by coupling 123 to the drive shaft 124 of wheel 120 rotatably supported on bearings 124.- Bearings 124 are advantageously mounted to a pivoted support member pivoted about pin 125 on base plate support 127 upon operation of hydraulic cylinder 129. Drive wheel assembly 118 and the support therefor are similar to the stress frame driving unit shown and described in U.S. Pat. No. 3,523,343.

Horizontal pallet 92 provided between adjacent leg depending members of each form serves to close off the bottom of the form, while the sides are closed off by suitable side form members 93 and 94 extending across outer upstanding vertical supports 95 and 96 which shape the sides of the outer arms of the slab. Form members 93, 95 are also provided in l0 to foot sectional lengths. The intermediate sections 132 of slab.

128 are supported by a plurality of upstanding vertical supports 97 secured at their lower ends to the stress frame.

Horizontal pallets 92 are each supported for displacement in substantially perpendicular directions. To this end, wheels 98 are carried by means of bracket 99 secured to the bottom of pallet 92 and form a roller assembly that rides on platform 100 which is adapted to be raised upon movement of the cam follower 101 along the stepped cam surface 102. lf desired, a suitable' movement limiting stop 188 may be provided as shown in FIG. 10. Stop 188 comprises a pair of link arms or members 189, 190 having one end pivoted about pin 191. The other end of link arm 190 is pivotally fastened to pin 192 secured to gusset plate 104, while the other end of link arm 189 is pivoted on a pin 193 fastened to bracket 195 which is in turn secured to a cross member 72. As should be apparent, several such stop assemblies may be provided to limit the extent of travel of the drive beam and relative movement between the cam follower 101 and cam surface 102.

As will be evident from the foregoing description in connection with FIG. 1, each of the operating units used in the production of the form member on the casting bed is stored individually on storage tracks when not in use. Each unit is moved individually and in sequence from its stored position to its operative position by means of transfer car 48. The manner in which the units are positioned and the manner in which such units operate in conjunction with a moving bed process are well known. For a detailed description of such units and their manner of operation, reference may be made to U.S. Pat. No. 3,523,343.

Referring now to FIGS. 4 and 5, there is illustrated therein the drive units by which the casting bed 14 is moved back and forth along track 22 as well as the drive unit by which the drive beam 117 is moved to raise the elevating mechanism and cast slab 128 above the form 82. The stress frame driving units are preferably located at suitable locations along fixed track 22, preferably adjacent the exits to the main building 10 and the exit of kiln 12. The drive unit by which beam 117 is driven to raise the horizontal pallet 92 is disposed in a pit 119 and between tracks 22 adjacent the exit of kiln 12 so as to enable the cured or cast product to be raised slightly above the height of the roller conveyor 16 as it leaves the kiln.

Each of the driving units must be capable of moving several hundred thousand pounds and, as shown in H6. 4, each driving unit comprises a variable speedreversible hydraulic motor 121. The stress frame driving motors are located on opposite sides of the track and in a pit between tracks 22. Each motor includes a drive shaft 122, one end of which is connected through couplings 123 to the end of a driven shaft to which is mounted rubber-tired wheels 120. Wheels have frictional engagement with the side members of the casting bed 14 and the drive beam 117 of the elevating mechanism. Each driven shaft 122 is rotatably supported in bearings 124, located on opposite sides of each wheel. Bearings 124 are fixed to a tubular pivoted support member 126.

With reference to P16. 4 and the tubular support members that drive the side members 76, the lower ends are connected to an inwardly inclined pipe section 138. The lower end is so shaped as to rest on the outer surface of a horizontally extending tubular member intermediate the ends thereof. The ends of member 140 are provided with eccentrically disposed pivot shafts 126 which are journalled in bearings 139 mounted on plate 141 secured to the foundation 142 of track rails 22. Each pair of plates 141 of opposite sides of the track are connected by a tension rod 143.

Mounted on the upper end of support members 126 are inwardly extending motor mounting plates 137 on which the motors 121 are supported and which also support a pair of upwardly extending beams 144. The beams 144 in turn support means which move the stress frame drive wheels 120 into and out of frictional engagement with the side members 76 of the casting bed and also control the amount of thrust exerted by the wheels against the side members.

In the embodiment illustrated this means comprises a hydraulic cylinder 146 having one end pivotally connected to the upper end of one of the beams 144 and a tension rod 148 connected to the piston rod 150 of cylinder 146 by turn buckle 152. The opposite end of the tension rod is threaded and passes clearly through a bracket in an opening 154 mounted on the upper end of the other beam 144, the outer end of the tension rod beyond the bracket carries spring 156, the pressure of which is adjustable by means of nuts 158 threaded on the extremity of thetension rod. The threaded portion of the tension rod 148 inwardly of bracket 157 is provided with a pair of stop nuts 160 so that movement of the tension rod to the left is viewed in FIG. 4 as transmitted to the left hand beam 144 and support member 126 to move the associated wheel 120 outwardly with respect to the casting bed. For the drive beam 117, cylinder 129 controls the amount of thrust exerted by drive wheel 120. Hydraulic pressure fluid may be supplied to either end of cylinder 129 and 146 from power unit 60 through suitable piping (not shown). Stop members 163, fixed to the foundation 142 are provided adjacent each pivoted support member 125 to limit the outward movement of the motor supporting members. When it is desired to engage the driving wheels with the associated beam, the hydraulic pressure is appliedto the one end of the corresponding cylinder so as to pull the motor supporting assembly away from the disengaged positions. The amount of thrust which the drivto maintain the amount of thrust substantially constant.

As hereinbefore indicated, the curing area is in the form of a kiln 12 of Quonset type construction and is best illustrated in FIG. 5. The kiln is normally open to the main manufacturing building 10 at its right hand end view in H6. 1 and closed at its opposite end just beyond the end of the track 22v by a sliding door. The curing operation takes place by means of steam or hot oil circulated through a series of pipes 166 which, as shown in FIG. 5, are suitably supported beneath the stress frame of the casting bed 14 between track rails 22 so as to produce the required curing temperature which is in the kiln. The kiln may also be provided with a plurality of unit heaters 168 supported above the casting bed at spaced intervals along the lengthof the kiln and with drop leaf dampers 170 which control the outflow of the air from the kiln through openings along the base of the kiln wall. If desired, the kiln may also be provided with a plurality of roof-mounted exhaust fans 172.

In order to confine the heated curing atmosphere to the immediate vicinity of the cast slab as it rests on the pallet 92, an insulating blanket 174 of any suitable material is suspended from the roof portion of the kiln directly above the casting bed by means of an angle iron framework 176, while the space along the sides of the pallet may be closed by curtains 178 of insulating in vapor-proof material. The upper ends of curtains 178 are fixed to the angle iron framework adjacent the side edges of the blanket 174, while the lower ends are fixed to the longitudinally extending channel irons 180 which are heavy enough to maintain the curtains in the vertical position illustrated in the left hand portion of FIG. 5 during the curing operation. Also connected to channel irons 180 at spaced points along the way thereof are a plurality of nylon sash cords 182, the upper ends of which are fixed to arbors 184 rotatably supported in bearings 186 carried by the angle iron framework 176. The arbors may be rotated in their bearings in any suitable manner as by electric switches (not shown) so as to raise and lower the curtains 178 as desired.

Although only one specific embodiment of the system of the present invention has been described and illustrated in the accompanying drawings, it will be apparent to those skilled in the art that various changes may be made in the details of construction of the vari-' ous elements of the system without departing from the inventive concept. For example, means other than thetransfer car shown, such as an overhead monorail device, may be used for sequentially moving the various equipment units into and out of their operating positions, and in lieu of using insulating, vapor-proof curtains around the plank during the curing operation, the jacking heads may be provided with suitable temperature responsive devices which maintain a constant tension on the prestressed strands in spite of wide variations in the temperature to which the stands are subje'cted during the curing operation. Reference is therefore to be had to the appended claims for a definitio of the scope of the invention.

We claim:

1. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68), a mold form (82) carried by said frame (68), said mold (82) form including at least a pair of vertically disposed spaced side members (84, 85, 86, 88) and a horiiontally disposed pallet member'(92) positioned between said side members and closing off the lower end of said form, means (98 for supporting said pallet member (92) for vertical movement between said side members and a horizontally movable cam and cooperating means (90, 91) connected to said side members, adjacent said lower end for springing said side members laterally away from one another at the lower end of the form upon movement of the cam to enable stripping of the cast structural member from the form upon vertical movement of the pallet member.

2. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68), a mold form (82) carried by said frame (68 said mold (82) form including at least a pair of vertically disposed spaced side members (84, 85, 86, 88) and a horizontally disposed pallet member (92) positioned between said side members and closing off the lower end of said form, means for supporting said pallet member (92) for vertical movement between said side members including a roller assembly (98) depending from said pallet, an elevating platform (100) supporting said roller assembly and means (101) connected to said platform and adapted to be actuated for elevating said platform and means (90, 91) connected to said side members, adjacent said lower end for springing said side members laterally away from one another at the lower end of the form to enable stripping of the cast structural member from the form upon vertical movement of the pallet member.

3. Apparatus for the production of cast concrete structural members as set forth in claim 2 wherein said .means (101) connected to said platform and adapted ment in a direction parallel to the length of said mold form.

4. Apparatus for the production of cast concrete structural members as set forth in claim 3 wherein said inclined cam member includes step portions (108, 109). t

5. Apparatus for the production of cast concrete structural members as set forth in claim 3 including a drive beam (117) supporting said cam member for movement and means for driving said beam to effect longitudinal movement of said cam.

6. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68), a mold form (82) carried by said frame (68), said mold (82) form including at least a pair of vertically disposed spaced side members (84, 85, 86, 88) and a horizontally disposed pallet member (92) positioned between said side members and closing off the lower end of said form, means (98) for supporting said pallet member (92) for vertical movement between said side members and means (90, 91) connected to said side members, adjacent said lower end for springing said side members laterally away from one another at the lower end of the form to enable stripping of the cast structural member from the form upon vertical movement of the pallet member, said means connected to said side members for springing said side members including at least one horizontally disposed cam plate (64), having oriented slots (63), pin members (91) supported to said side members and extending through said slots and means (69) for moving said cam plate in a horizontal plane.

7. Apparatus for the production of cast concrete structural members as set forth in claim 6 wherein each said side members includes a plurality of spaced pin members (91), and further including a plurality of horizontally disposed cam plates (64) supported in spaced relationship beneath said side members, each cam plate having oppositely oriented diagonal slots (62) adapted to receive therein said pin members.

8. Apparatus for the production of cast concrete structural members'comprising a casting bed including a stress frame, a mold form carried by said stress frame, said mold form including a pair of longitudinally extending, vertically disposed spaced members, a horizontally disposed pallet member extending the length of said side members and being supported between said side members at the lower end thereof to close off said lower end of said form, means for supporting said pallet member for vertical movement between said side members, a plurality of spaced reinforcing ribs connected to said side members, bracket means supported at the lower end of said side members, a plurality of spaced pin members depending from said bracket means, a cam plate disposed beneath said mold form, and movable along the longitudinal axis of said spaced members, said cam plate having oppositely oriented diagonal slots adapted to receive depending pin members for springing said side members laterally away from one another at the lower end of the form upon longitudinal movement of said cam plate.

9. Apparatus for the production of cast concrete structural members as set forth in claim 8 wherein said means for supporting said pallet member includes a roller assembly depending from said pallet, an elevating platform supporting said roller assembly and means connected to said platform and adapted to be actuated for elevating said platform.

10. Apparatus for the production of cast concrete structural members as set forth in claim 9 wherein said means connected to said platform and adapted to be actuated for elevating said platform includes a cam follower depending from said platform and cooperating with an inclined cam member, said cam member being supported for longitudinal movement in a direction parallel to the length of said mold form.

11. Apparatus for the production of cast concrete structural members as set forth in claim 10 wherein said inclined cam member includes step portions.

12. Apparatus for the production of cast concrete structural members as set forth in claim 10 including a drive beam supporting said cam member for movement and means for driving said beam to effect longitudinal movement of said cam.

13. Apparatus for the production of cast concrete structural members comprising a casting bed including a stress frame, a mold form'carried by said frame, said mold form including a pair of inverted L-shape sections having oppositely disposed horizontally extending arm members and spaced vertically extending side members and a horizontally disposed pallet member positioned between said side members for closing off the lower end of the mold form, means for supporting said pallet member for movement in vertical and horizontal directions and means connected to said side members adjacent said lower end of said form for springing said side members laterally away from one another to enable stripping of a cast structural member from the form upon movement of the pallet member in the vertical direction.

14. Apparatus for the production of cast concrete structural members as set forth in claim 13 wherein said means for supporting said pallet member for movement in said vertical and horizontal directions includes a roller assembly depending from said pallet and an elevating platform supporting said roller assembly including means connected to said platform and adapted to be actuated for elevating said platform in the vertical direction, said roller assembly being disposed on the top surface of said platform to enable movement of the pallet in a longitudinal horizontal direction.

15. Apparatus for the production of cast concrete structural members as set forth in claim 14 wherein said means connected to said platform and-adapted to be actuated for elevating said platform includes a plurality of spaced cam followers depending from said platform, each cooperating with an associated inclined cam member, said cam members being supported for longitudinal movement in a direction parallel to the length of said mold form.

16. Apparatus for the production of cast concrete structural members as set forth in claim 15 wherein said inclined cam members include step portions.

17. Apparatus for the production of cast concrete structural members as set forth in claim 15 including a drive beam supporting said cam member for movement, means for driving said beam to effect longitudinal movement of said cam and an overtravel link connected between said drive beam and said cam follower to limit travel of said cam members relative to said cam followers.

18. Apparatus for the production of cast concrete structural members as set forth in claim 13 wherein said means connected to said side members for springing said side members includes at least one cam plate, horizontally disposed below said side plates and having oriented slots, pin members supported to said side members and extending through said slots and means for moving said cam plate in a horizontal plane to thereby effect lateral movement of the side members.

19. Apparatus for the production of cast concrete structural members as set forth in claim 18 wherein each said side members includes a plurality of spaced pin members, and further including a plurality of horizontally disposed cam plates supported in spaced relationship beneath said side members, each cam plate having oppositely oriented diagonal slots adapted to receive therein pin members.

20. Apparatus for the production of cast concrete structural members comprising a casting bed including a longitudinal extending stress frame, a longitudinally extending mold form carried by said frame, said mold form including a plurality of inverted L-shaped sections, each having a horizontally extending member and a vertically oriented member, said sections being arranged with horizontal members of at least two first sections extending in opposite directions and abutting each other at their free ends and at least two additional L-shape sections, one each disposed on opposite sides of said first two sections with the vertically oriented members in spaced relationship so as to provide a mold form for casting concrete structural members having a cross-section comprising a plurality of vertical stems and a joining horizontal platform, a horizontally disposed pallet member positioned between adjacent vertically oriented members for closing off the space there between at the lower end thereof, means for supporting said pallet member for movement in vertical and horizontal directions and means connected to said adjacent vertically oriented members for springing said members laterally away from one another to enable stripping of a cast structural member from the form upon elevation of said pallet member.

21. Apparatus for the production of cast concrete structural members as set forth in claim 20 wherein said means for supporting said pallet member for movement in said vertical and horizontal directions includes a roller assembly depending from said pallet and an elevating platform assembly supporting said roller assembly and actuating means connected to said platform assembly and adapted to be actuated for elevating said platform in a vertical direction, said roller assembly being disposed on the top surface of said platform to facilitate transfer of the pallet in a longitudinal direction to another position along said platfonn.

22. Apparatus for the production of cast concrete structural members as set forth in claim 21 wherein said means connected to said platform and adapted to be actuated for elevating said platfonn includes a plurality of spaced cam followers. depending from said platform, each follower cooperating with an associated inclined cam member, said cam member being supported for longitudinal movement in the direction parallel to the length of said mold form.

23. Apparatus for the production of cast concrete structural members as set forth in claim 22 wherein said cam members include a plurality of horizontally disposed step portions.

24. Apparatus for the production of cast concrete structural members as set forth in claim 22 including a longitudinally movable drive beam supporting said cam members, means for driving said beam to effect longitudinal movement of said cams and an overtravel link connected between said drive beam and at least one of said cam followers to limit travel of said cam member relative to said followers.

25. Apparatus for the production of cast concrete structural members as set forth in claim 20, wherein said means connected to said side members for springing said vertically oriented members includes at least one cam plate, said cam plate being horizontally disposed below said vertically oriented members and having a slot associated with each said member, means depending from each said member and extending through an associated slot and drive means for moving said cam plate in a horizontal plate to thereby effect lateral movement of adjacent vertically oriented members away from one another.

26. Apparatus for the production of cast concrete structural members as set forth in claim 25 wherein each said vertically oriented member includes a plurality of longitudinally spaced pin members'and further including a plurality of horizontally disposed cam plates supported in a longitudinally spaced relationship beneath said oriented members in cooperative association with said pin members, each cam plate having pairs of oppositely oriented diagonal slots adapted to receive therein pin members of adjacent vertically oriented members.

27. Apparatus 'for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68) and a mold form (82) carried by'said stress frame (68), said mold from (82) including a pair of longitudinally extending, verti-' cally disposed spaced members (84, 85, 86, 88), a horizontally disposed pallet member (92) extending the length of said side members (84, 85, 86, 88) and being supported between said side members at the lower end thereof to close off the lower end of said form, a roller assembly (98) depending from said pallet member (92) and supporting said pallet member for vertical movement between said side members (84, 85, 86, 88), a plurality of spaced reinforcing ribs 89 connected to said side members, brackets (90) supported at the lower end of said side members, a plurality of spaced pin members (91) depending from said brackets (90), a longitudinally movable cam plate (64) disposed beneath said mold form (82), said cam plate (64) having oppositely oriented diagonal slots (63) adapted to receive depending pin members (91) for springing said side members (84, 85, 86, 88) laterally away from one another at their lower ends upon longitudinal movement of said cam plate (64).

28. Apparatus for the production of cast concrete structural members as set forth in claim 27 further including an elevating platform supporting said roller assembly (98) and a cam follower (101) depending from said platform (100) and cooperating with an inclined cam member (102), said cam member (102) being supported for longitudinal movement in a direction parallel to the length of said mold form for elevating said platform (100) upon movement of said cam member (102).

29. Apparatus for the production of cast concrete structural members as set forth in claim 28 wherein drive beam (113) supporting said cam member (102) for longitudinal movement of said cam member (102).

31. Apparatus for the production of cast concrete structural members as set forth in claim 30 further including an overtravel link (188) connected between said drive beam (113) and said cam follower (101) to limit travel of said cam member (102) relative to said cam follower (101).

$232 3 UNITED STATES PATENT OFFICE 1 I @ERTIFICATE OF CORRECTION Patent No. 3 327 1 g Dated juglc'f' 37" 1974 1nventor(s) William E. Mitchell It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

I On the title page, cancel "Leonard et a1.

Claim 7, column 11, line 40, "62" should be 63-- Claim 20, column 13, line 19, "longitudinal" should be longitudinally-- Signed and sealed this 5th day of November-1974.

(SEAL) Attest: I r

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commlssloner of Patents 

1. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68), a mold form (82) carried by said frame (68), said mold (82) form including at least a pair of vertically disposed spaced side members (84, 85, 86, 88) and a horizontally disposed pallet member (92) positioned between said side members and closing off the lower end of said form, means (98) for supporting said pallet member (92) for vertical movement between said side members and a horizontally movable cam and cooperating means (90, 91) connected to said side members, adjacent said lower end for springing said side members laterally away from one another at the lower end of the form upon movement of the cam to enable stripping of the cast structural member from the form upon vertical movement of the pallet member.
 2. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68), a mold form (82) carried by said frame (68), said mold (82) form including at least a pair of vertically disposed spaced side members (84, 85, 86, 88) and a horizontally disposed pallet member (92) positioned between said side members and closing off the lower end of said form, means for supporting said pallet member (92) for vertical movement between said side members including a roller assembly (98) depending from said pallet, an elevating platform (100) supporting said roller assembly and means (101) connected to said platform and adapted to be actuated for elevating said platform and means (90, 91) connected to said side members, adjacent said lower end for springing said side members laterally away from one another at the lower end of the form to enable stripping of the cast structural member from the form upon vertical movement of the pallet member.
 3. Apparatus for the production of cast concrete structural members as set forth in claim 2 wherein said means (101) connected to said platform and adapted to be actuated for elevating said platform includes a cam follower (101) depending from said platform and cooperating with an inclined cam member (102), said cam member being supported for longitudinal movement in a direction parallel to the length of said mold form.
 4. Apparatus for the production of cast concrete structural members as set forth in claim 3 wherein said inclined cam member includes step portions (108, 109).
 5. AppAratus for the production of cast concrete structural members as set forth in claim 3 including a drive beam (117) supporting said cam member for movement and means for driving said beam to effect longitudinal movement of said cam.
 6. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68), a mold form (82) carried by said frame (68), said mold (82) form including at least a pair of vertically disposed spaced side members (84, 85, 86, 88) and a horizontally disposed pallet member (92) positioned between said side members and closing off the lower end of said form, means (98) for supporting said pallet member (92) for vertical movement between said side members and means (90, 91) connected to said side members, adjacent said lower end for springing said side members laterally away from one another at the lower end of the form to enable stripping of the cast structural member from the form upon vertical movement of the pallet member, said means connected to said side members for springing said side members including at least one horizontally disposed cam plate (64), having oriented slots (63), pin members (91) supported to said side members and extending through said slots and means (69) for moving said cam plate in a horizontal plane.
 7. Apparatus for the production of cast concrete structural members as set forth in claim 6 wherein each said side members includes a plurality of spaced pin members (91), and further including a plurality of horizontally disposed cam plates (64) supported in spaced relationship beneath said side members, each cam plate having oppositely oriented diagonal slots (62) adapted to receive therein said pin members.
 8. Apparatus for the production of cast concrete structural members comprising a casting bed including a stress frame, a mold form carried by said stress frame, said mold form including a pair of longitudinally extending, vertically disposed spaced members, a horizontally disposed pallet member extending the length of said side members and being supported between said side members at the lower end thereof to close off said lower end of said form, means for supporting said pallet member for vertical movement between said side members, a plurality of spaced reinforcing ribs connected to said side members, bracket means supported at the lower end of said side members, a plurality of spaced pin members depending from said bracket means, a cam plate disposed beneath said mold form, and movable along the longitudinal axis of said spaced members, said cam plate having oppositely oriented diagonal slots adapted to receive depending pin members for springing said side members laterally away from one another at the lower end of the form upon longitudinal movement of said cam plate.
 9. Apparatus for the production of cast concrete structural members as set forth in claim 8 wherein said means for supporting said pallet member includes a roller assembly depending from said pallet, an elevating platform supporting said roller assembly and means connected to said platform and adapted to be actuated for elevating said platform.
 10. Apparatus for the production of cast concrete structural members as set forth in claim 9 wherein said means connected to said platform and adapted to be actuated for elevating said platform includes a cam follower depending from said platform and cooperating with an inclined cam member, said cam member being supported for longitudinal movement in a direction parallel to the length of said mold form.
 11. Apparatus for the production of cast concrete structural members as set forth in claim 10 wherein said inclined cam member includes step portions.
 12. Apparatus for the production of cast concrete structural members as set forth in claim 10 including a drive beam supporting said cam member for movement and means for driving said beam to effect longitudinal movement of said cam.
 13. Apparatus for the productIon of cast concrete structural members comprising a casting bed including a stress frame, a mold form carried by said frame, said mold form including a pair of inverted L-shape sections having oppositely disposed horizontally extending arm members and spaced vertically extending side members and a horizontally disposed pallet member positioned between said side members for closing off the lower end of the mold form, means for supporting said pallet member for movement in vertical and horizontal directions and means connected to said side members adjacent said lower end of said form for springing said side members laterally away from one another to enable stripping of a cast structural member from the form upon movement of the pallet member in the vertical direction.
 14. Apparatus for the production of cast concrete structural members as set forth in claim 13 wherein said means for supporting said pallet member for movement in said vertical and horizontal directions includes a roller assembly depending from said pallet and an elevating platform supporting said roller assembly including means connected to said platform and adapted to be actuated for elevating said platform in the vertical direction, said roller assembly being disposed on the top surface of said platform to enable movement of the pallet in a longitudinal horizontal direction.
 15. Apparatus for the production of cast concrete structural members as set forth in claim 14 wherein said means connected to said platform and adapted to be actuated for elevating said platform includes a plurality of spaced cam followers depending from said platform, each cooperating with an associated inclined cam member, said cam members being supported for longitudinal movement in a direction parallel to the length of said mold form.
 16. Apparatus for the production of cast concrete structural members as set forth in claim 15 wherein said inclined cam members include step portions.
 17. Apparatus for the production of cast concrete structural members as set forth in claim 15 including a drive beam supporting said cam member for movement, means for driving said beam to effect longitudinal movement of said cam and an overtravel link connected between said drive beam and said cam follower to limit travel of said cam members relative to said cam followers.
 18. Apparatus for the production of cast concrete structural members as set forth in claim 13 wherein said means connected to said side members for springing said side members includes at least one cam plate, horizontally disposed below said side plates and having oriented slots, pin members supported to said side members and extending through said slots and means for moving said cam plate in a horizontal plane to thereby effect lateral movement of the side members.
 19. Apparatus for the production of cast concrete structural members as set forth in claim 18 wherein each said side members includes a plurality of spaced pin members, and further including a plurality of horizontally disposed cam plates supported in spaced relationship beneath said side members, each cam plate having oppositely oriented diagonal slots adapted to receive therein pin members.
 20. Apparatus for the production of cast concrete structural members comprising a casting bed including a longitudinal extending stress frame, a longitudinally extending mold form carried by said frame, said mold form including a plurality of inverted L-shaped sections, each having a horizontally extending member and a vertically oriented member, said sections being arranged with horizontal members of at least two first sections extending in opposite directions and abutting each other at their free ends and at least two additional L-shape sections, one each disposed on opposite sides of said first two sections with the vertically oriented members in spaced relationship so as to provide a mold form for casting concrete structural members having a cross-section comprising a plurality of vertical stEms and a joining horizontal platform, a horizontally disposed pallet member positioned between adjacent vertically oriented members for closing off the space there between at the lower end thereof, means for supporting said pallet member for movement in vertical and horizontal directions and means connected to said adjacent vertically oriented members for springing said members laterally away from one another to enable stripping of a cast structural member from the form upon elevation of said pallet member.
 21. Apparatus for the production of cast concrete structural members as set forth in claim 20 wherein said means for supporting said pallet member for movement in said vertical and horizontal directions includes a roller assembly depending from said pallet and an elevating platform assembly supporting said roller assembly and actuating means connected to said platform assembly and adapted to be actuated for elevating said platform in a vertical direction, said roller assembly being disposed on the top surface of said platform to facilitate transfer of the pallet in a longitudinal direction to another position along said platform.
 22. Apparatus for the production of cast concrete structural members as set forth in claim 21 wherein said means connected to said platform and adapted to be actuated for elevating said platform includes a plurality of spaced cam followers depending from said platform, each follower cooperating with an associated inclined cam member, said cam member being supported for longitudinal movement in the direction parallel to the length of said mold form.
 23. Apparatus for the production of cast concrete structural members as set forth in claim 22 wherein said cam members include a plurality of horizontally disposed step portions.
 24. Apparatus for the production of cast concrete structural members as set forth in claim 22 including a longitudinally movable drive beam supporting said cam members, means for driving said beam to effect longitudinal movement of said cams and an overtravel link connected between said drive beam and at least one of said cam followers to limit travel of said cam member relative to said followers.
 25. Apparatus for the production of cast concrete structural members as set forth in claim 20, wherein said means connected to said side members for springing said vertically oriented members includes at least one cam plate, said cam plate being horizontally disposed below said vertically oriented members and having a slot associated with each said member, means depending from each said member and extending through an associated slot and drive means for moving said cam plate in a horizontal plate to thereby effect lateral movement of adjacent vertically oriented members away from one another.
 26. Apparatus for the production of cast concrete structural members as set forth in claim 25 wherein each said vertically oriented member includes a plurality of longitudinally spaced pin members and further including a plurality of horizontally disposed cam plates supported in a longitudinally spaced relationship beneath said oriented members in cooperative association with said pin members, each cam plate having pairs of oppositely oriented diagonal slots adapted to receive therein pin members of adjacent vertically oriented members.
 27. Apparatus for the production of cast concrete structural members in a form comprising a casting bed (14) including a stress frame (68) and a mold form (82) carried by said stress frame (68), said mold from (82) including a pair of longitudinally extending, vertically disposed spaced members (84, 85, 86, 88), a horizontally disposed pallet member (92) extending the length of said side members (84, 85, 86, 88) and being supported between said side members at the lower end thereof to close off the lower end of said form, a roller assembly (98) depending from said pallet member (92) and supporting said pallet member for vertical movement between said side members (84, 85, 86, 88), a plurality of spaced reinforcing ribs 89 connected to said side members, brackets (90) supported at the lower end of said side members, a plurality of spaced pin members (91) depending from said brackets (90), a longitudinally movable cam plate (64) disposed beneath said mold form (82), said cam plate (64) having oppositely oriented diagonal slots (63) adapted to receive depending pin members (91) for springing said side members (84, 85, 86, 88) laterally away from one another at their lower ends upon longitudinal movement of said cam plate (64).
 28. Apparatus for the production of cast concrete structural members as set forth in claim 27 further including an elevating platform (100) supporting said roller assembly (98) and a cam follower (101) depending from said platform (100) and cooperating with an inclined cam member (102), said cam member (102) being supported for longitudinal movement in a direction parallel to the length of said mold form for elevating said platform (100) upon movement of said cam member (102).
 29. Apparatus for the production of cast concrete structural members as set forth in claim 28 wherein said inclined cam member includes step portions (108, 109, 110).
 30. Apparatus for the production of cast concrete structural members as set forth in claim 29 including a drive beam (113) supporting said cam member (102) for longitudinal movement of said cam member (102).
 31. Apparatus for the production of cast concrete structural members as set forth in claim 30 further including an overtravel link (188) connected between said drive beam (113) and said cam follower (101) to limit travel of said cam member (102) relative to said cam follower (101). 